This invention relates to automated welding apparatus, and more particularly to a device to detect coolant leakage and automatically shut off a coolant supply valve in response thereto.
Automated welding systems, either xe2x80x9chardxe2x80x9d automated systems or robotic arms fitted with welding end-of-arm units, are now in common use in many types of manufacturing. The heat generated by automated welding systems is sufficiently great that a source of forced cooling is required. Typically, automated welding units are liquid-cooled, with coolant (typically water) being supplied from a source of pressurized coolant remote from the welding unit. In many installations, a large number of automated welding machines are plumbed to a common source of coolant liquid under pressure.
The typical coolant flow through an automated spot-welding gun, a common variant, is about six gallons per minute. Tie SCR weld control is typically supplied 1-2 gpm, the weld gun upper tip 1.5 gpm, weld gun lower tip 1.5 gpm, the shunts 1 gpm, and the cable 1.5 gpm. The usage of a liquid coolant with high-powered electrical equipment necessitates some sort of safety system to detect coolant leakage in the event of broken coolant lines or other failures in the coolant system. In addition, it is desirable to detect either excessive flow or insufficient flow conditions. An excessive flow condition can mean that coolant supply pressure has exceeded its design level or that a necessary restriction within the cooling system has been removed. Similarly, an insufficient flow condition can indicate a failure of the coolant supply or a general blockage of the coolant supply or return lines.
Present solutions to the requirement of sensing and monitoring coolant flow in automated welding arms have used complicated and expensive mechanical leakage detection devices. For example, a water control valve manufactured by Norco of Troy, Michigan relies on a complicated spool valve having opposed surfaces on opposite sides of the flow circuit to sense pressure imbalances. Numerous o-rings, diaphragms and moving parts make reliable operation of this device as questionable as the proper operation of the cooling system it is designed to protect. Thus, in addition to the expense of such a system, there are concerns about the maintenance and reliability of the prior art safety systems.
Thus, there presently exists a need for a coolant safety system for an automated welding machine that is simple, inexpensive and reliable with minimal maintenance requirements. Furthermore, there is a need for coolant safety system for an automated welding machine that includes an auxiliary sensor on board, a multi gun unit, and an easily programmable unit for different welding applications.
The present invention provides a coolant system safety device for an automated welding machine that combines electronic control by way of a microprocessor with flow level and leakage detection provided by inexpensive yet reliable differential pressure transmitters. An integral digital flow rate display is also provided.